Our new method for the large scale fractionation of Drosophila egg chambers makes it possible to study biochemical events during Drosophila oogenesis. The availability of this method makes Drosophila a choice organism for the study of oogenesis in general, for the study on how the egg prepares itself for the extremely fast events of early embryogenesis and very importantly provides the possibility of linking biochemistry to genetics in the study of early development. The following aspects shall be examined: a) Study of the regulation of transcription and translation of the genes coding for histones, actin and tubulin. These proteins and the corresponding mRNAs shall be quantitated in egg chambers of different developmental stages and in unfertilized eggs. We shall also distinguish between mRNAs associated with ribonucleoprotein particles (stored mRNA) and with polysomes (active mRNA). These measurements should provide extensive information on the dynamics of synthesis and storage of specific gene products. b) Large amounts of DNA are accumulated in the nurse cell nuclei during oogenesis. We propose to examine the fate of this DNA by radiolabeling it during oogenesis and investigating in which form, if at all, it is found in the unfertilized egg. It is hoped that the understanding of oogenesis at a biochemical level will provide some keys for the evident link between the egg and the embryo.